A polymer electrolyte fuel cell typically comprises a membrane electrode assembly (to be referred to as an “MEA” hereafter), and a pair of separators laminated onto either surface of the MEA. The MEA comprises an electrolyte membrane, an anode formed on one surface of the electrolyte membrane, and a cathode formed on the other surface of the electrolyte membrane. The output voltage of a single fuel cell is low, and therefore a large number of fuel cells are typically laminated to each other for use as a fuel cell stack.
A hydrogen (H2) passage is formed in the separator facing the anode. An anode gas containing a large amount of hydrogen is supplied to the hydrogen passage. An oxygen (O2) passage is formed in the separator facing the cathode. A cathode gas containing a large amount of oxygen is supplied to the oxygen passage. The hydrogen (H2) that contacts the anode emits an electron (e+), then forms a hydrogen ion (H+) that passes through the electrolyte membrane and moves to the cathode. The flow of emitted electrons (e+) forms the output of the fuel cell.
Thus, the anode gas and cathode gas flow along the passages in the separators while contacting the anode and cathode. To prevent the anode gas and cathode gas from leaking out of the fuel cell, a sealing member is sandwiched between the separator and the electrolyte membrane.
When fuel cells are laminated into a fuel cell stack, the sealing member sandwiched between the separator and the electrolyte membrane remains tightly adhered to the separator and electrolyte membrane while deforming elastically. The elastically deformed sealing member applies a repulsive force to the separator and electrolyte membrane. In the following description, this repulsive force generated by the elastically deformed sealing member will be referred to as a sealing reactive force.
The electrolyte membrane is less rigid than the separator and is therefore easily deformed by the sealing reactive force. However, when the electrolyte membrane deforms, the sealing performance of the sealing member deteriorates.